Human and Chimpanzee Natural Cognition

By Christophe Boesch

Philosophers, anthropologists, psychologists and others have been addressing the question of “What makes us humans?” for centuries. However, we have always been limited in our ability to answer that question by the fact that in most comparative studies either humans and/or chimpanzees, our closest living relatives, have been placed in speciesunnatural conditions or have been tested in species untypical situations. Thereby, either species were facing a systematic disadvantage that has hampered our ability to understand “What makes us humans?”

In theory, the solution to this quandary is rather straightforward, as it would “only” require to select some natural tasks that are performed by both species and to compare them in situ. My goal in this project is to do exactly this and compare humans with chimpanzees solving two similar natural tasks: Finding food producing trees in their natural environment and cracking wild nuts.

By making the human / chimpanzee comparison with natural populations solving similar natural daily tasks with all their local and historical accumulated knowledge of the technical challenge, we hope to be able to detect more precisely species differences that are only affected by the specie-specific way to solve such ecological challenges.

Finding food producing trees

Finding food trees is a basic challenge that all animals including humans have to solve and this challenge might be complicated by the visibility conditions prevailing in different environments. Therefore, we are comparing the food finding strategies of the Hadza people in Tanzania, living in an open dry savannah environment, as well as those of the Aka foragers in Central African Republic, living in a closed tropical rainforest, with those of the Taï chimpanzees in Côte d’Ivoire, also living in a closed tropical rainforest.

Our methods for this comparison will be based on the work we have been doing for some years now on the Taï chimpanzees (see our publications Normand et al. 2009a, b, in press, Janmaat et al. 2013, in press). Adopting exactly the same methodology for a similar natural task should allow us to progress our knowledge of the similarities and differences between humans and chimpanzees, as well as try to approach the importance of the ecology on such aspects.

This project is done in collaboration with Frank Marlowe of the University of Cambridge, UK, for the Hadza part, and for the Aka foragers part in collaboration with Barry Hewlett and Adam Boyette of the Washington State University, USA.

Figure 1: A group of Hadza women in the dry savannah is arriving at a Baobab, a major food resource for many months of the year tree

Figure 2: A group of Aka women is processing Irvingia nuts under the tree in the dense tropical forest, a major food for three months of the year.

Cracking wild nuts

Central African forest hunter-gatherers have traditionally been dependant to a large proportion on the many wild food produced by the forest. One of those resources is especially promising for comparing human and chimpanzee technological skills and this is the hard-shelled wild nuts. More specifically, the Aka foragers in the Central African Republic rely for many months of the year on the nuts they find and crack in the forest, many of those nut species being the same than the ones cracked by the Taï chimpanzees in Côte d’Ivoire. This will allow a very precise comparison of the technique used, the tool used and made, the transport of tools, the efficiencies reach with their tools and techniques, and the cognitive skills required in both species.

I have been studying the nut-cracking behaviour of the chimpanzees for many years and have extensively published about it (e.g. Boesch and Boesch 1981, 1982, 1984a, b, Boesch and Boesch-Achermann 2000, Boesch 1991, 2012). Adopting for this comparative project the same methodology while following Aka women foraging in the forest, I hope to make a detailed comparison of the similarities and the differences of the two species when facing extremely similar natural challenges involving tools.

Figure 3: An Aka mother cracking a Panda nut within the forest with her wooden hammer and an axe as anvil while her baby is looking over her shoulder at what she is doing.

Figure 4: A Taï chimpanzee mother cracking a Coula nut within the forest with a wooden hammer and a root as anvil, while her infant is looking intently at what she is doing